Method of improving viscosity stability upon addition of an aqueous tinting composition

ABSTRACT

An aqueous tinting composition containing a pigment and a select dispersing resin is disclosed. In addition, a method of improving the viscosity stability of an aqueous coating composition upon the addition of the aqueous tinting composition containing a pigment and a select dispersing resin is disclosed.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

This is a non-provisional application of prior pending U.S. provisionalapplication Ser. No. 60/271,992 filed on Feb. 28, 2001 and prior pendingU.S. provisional application Ser. No. 60/271,997 filed on Feb. 28, 2001.

This invention relates to an aqueous tinting composition containing apigment and a select dispersing resin. The aqueous tinting compositionis useful for tinting an aqueous base paint to prepare an aqueouscoating composition. A method is also provided for improving theviscosity stability of an aqueous coating composition upon the additionof the aqueous tinting composition.

A classic problem in paints is a decrease in the paint viscosity, inparticular, a decrease in mid-shear viscosity (Krebs-Stormer viscosity),when colorants that contain high levels of surfactant are added. This isespecially problematic when the paint is tinted to a deep tone because ahigh level of surfactant generally accompanies the colorant. Besidessurfactants, the colorants also contain other low molecular materialssuch as dispersants. The addition of colorants thus provides a source oflow molecular weight materials to the paint base. The properties ofcoatings prepared from paints may be adversely affected by the presenceof low molecular weight materials, for example, the films may becomewater sensitive.

Many paints are formulated with associative thickeners. Associativethickeners are water-soluble or water-swellable polymers that havechemically attached hydrophobic groups. The associative thickenersoperate to thicken systems to which they are added by the non-specificassociations, such as adsorption on surfaces and aggregation in solutionakin to micellization, between the hydrophobic groups on the thickenermolecules and moieties on the other components in the system, similar tothe non-specific associations of conventional surfactants. Paintsformulated with associative thickeners are especially sensitive to theproblem of a decrease in viscosity upon the addition of colorantscontaining high levels of surfactant.

WO 00/22050 discloses an universal tinting concentrate containing anorganic acid having no more than 70 carbon atoms. The disclosed tintingcomposition is suitable for water based paints. The addition of thistinting concentrate adds the organic acid having no more than 70 carbonatoms to the paint. This organic acid is a low molecular weight materialand may adversely affect film properties.

Colorants are added to paints in units of milliliter of colorant perliter of paint (hereinafter referred to as “ml/liter”) or ounces ofcolorant per gallon of paint (hereinafter referred to as “oz/gal”).Light-tint (pastel) paints typically contain no more than 31.2 ml/liter(4 oz/gal of colorant). Mid-tone paints typically contain from greaterthan 31.2 ml/liter (4 oz/gal of colorant) to 62.5 ml/liter (8 oz/gal) ofcolorant. Deep tone paints typically contain at least 62.5 ml/liter (8oz/gal) of colorant.

Generally, it is possible to formulate a light tint base at a highenough mid-shear viscosity that colorants added to it will not depressthe viscosity to an unacceptable degree. Combinations of associativethickeners have been found to be less sensitive to colorant additionthan the individual thickeners alone, in some cases. However, neither ofthese solutions is completely satisfactory because they either requiretedious reformulation, added cost or both, particularly in deep tonepaints.

Many conventional tinting machines employ twelve different colorants tomix the large palette of colors typically offered for most paint lines.Thus, it would be highly desirable to tailor the viscosity stability ofan aqueous formulation based on the type and level of colorant componentto be added, in particular, without the introduction of low molecularweight materials which may materially affect film properties. Thecompositions and methods of the present invention provide such asolution.

The first aspect of this invention provides a method of improving theviscosity stability of an aqueous coating composition upon the additionof an aqueous tinting composition, including the steps of: providing anaqueous base paint containing at least one polymer binder and at leastone rheology modifier; and adding to the aqueous base paint, the aqueoustinting composition containing at least one pigment and at least oneselect dispersing resin having a Hansch parameter in the range of 2.1 to6 and an acid number in the range of 65 to 150.

The second aspect of this invention provides an aqueous tintingcomposition containing from 2 to 70 weight % of at least one pigment,and from 0.1 to 40 weight % of at least one select dispersing resinhaving a Hansch parameter in the range of 2.1 to 6 and an acid number inthe range of 65 to 150, based on the weight of the aqueous tintingcomposition.

As used herein, the term “(meth)acrylate” refers to either acrylate ormethacrylate and the term “(meth)acrylic” refers to either acrylic ormethacrylic.

As used herein, pigment volume concentration (referred to herein as“PVC”) is a measure of how “binder-rich” a formulation is. It iscalculated herein by the following formula:${PVC} = {100\% \times \frac{( {{{volume}\quad {of}\quad {{pigments}(s)}} + {{volume}\quad {of}\quad {{extender}(s)}}} )}{\begin{matrix}( {{{volume}\quad {of}\quad {{pigments}(s)}} + {{volume}\quad {of}\quad {{extender}(s)}} +}  \\ {{volume}\quad {of}\quad {{binder}(s)}} )\end{matrix}}}$

As used herein, volume solids content (“VS” herein) is the dry volume ofpigment(s) plus the dry volume of extender(s) plus the dry volume ofbinder(s). It is calculated herein by the following formula:${VS} = {100\% \times \frac{\begin{matrix}( {{{dry}\quad {volume}\quad {of}\quad {{pigments}(s)}} + {{dry}\quad {volume}\quad {of}\quad {extender}(s)} +}  \\ {{dry}\quad {volume}\quad {of}\quad {{binder}(s)}} )\end{matrix}}{( {{total}\quad {volume}\quad {of}\quad {formulation}} )}}$

If additives are present, their volume is not included in determiningthe total dry volume.

As used herein, “KU” shall mean Krebs unit and is a measure of themid-shear viscosity as measured by a Krebs-Stormer viscometer.

As used herein, “viscosity stability” shall mean the ability of acomposition to resist change in viscosity as measured by KU upon theaddition of surfactant or a composition containing surfactant. Apreferred viscosity stabilizer for latex paints must provide KUviscosity changes of less than about 10 units upon the addition of up to93.7 ml/liter (12 oz/gal) of colorant. A more preferred viscositystabilizer for latex paints must provide KU viscosity changes of lessthan about 5 units upon the addition of up to 93.7 mi/liter (12 oz/gal)of colorant.

As used herein, a “volatile organic compound” (VOC) is defined herein asa carbon containing compound that has a boiling point below 280° C. atatmospheric pressure, compounds such as water and ammonia being excludedfrom VOCs. A volatile organic compound (VOC) may be added to an aqueouscoating composition to improve the film properties or to aid in theapplication properties of the aqueous coating composition. Examples ofsuch compounds include solvents and coalescents such as glycol ethers,organic esters, aromatic compounds, ethylene and propylene glycol, andaliphatic hydrocarbons.

The aqueous tinting composition of this invention contains at least onepigment and at least one select dispersing resin. The pigment isdispersed in the aqueous medium of the tinting composition.

The pigment is any organic or inorganic dry powder that imparts color toanother substance or mixture. Examples of suitable pigments includetitanium dioxide white, carbon black, lamp black, black iron oxide, rediron oxide, yellow iron oxide, brown iron oxide (a blend of red andyellow oxide with black), phthalocyanine green, phthalocyanine blue,organic red pigment (such as naphthol red, quinacridone red andtoulidine red), quinacridone magenta, quinacridone violet, DNA orange,organic yellow pigment (such as Hansa yellow), and combinations thereof.Another type of pigment is a “metal effect agent”, which impartsmetallic-type luster and associated properties to final drycompositions. An example of a suitable metal effect agent includes micahaving a titanium dioxide coating. The aqueous tinting composition maycontain from 2 to 70 weight %, preferably at least 3 to 65 weight %, andmore preferably, at least 4 to 63 weight % of at least one pigment,based on the weight of the aqueous tinting composition. The level ofpigment in the aqueous tinting composition depends upon the pigmenttype.

The aqueous tinting composition also contains a select dispersing resinto disperse the pigment in the aqueous medium. The select dispersingresin is an addition polymer having acid groups. The select dispersingresin may be prepared by the polymerization of ethylenically unsaturatedmonomers. Suitable monomers to prepare the select dispersing resininclude carboxylic acid monomers such as (meth)acrylic acid, itaconicacid, fumaric acid, and maleic acid; and comonomers such as includestyrene, butadiene, α-methyl styrene, vinyl toluene, vinyl naphthalene,ethylene, propylene, vinyl acetate, vinyl versatate, vinyl chloride,vinylidene chloride, acrylonitrile, methacrylonitrile, (meth)acrylamide,various C₁-C₄₀ alkyl esters of (meth)acrylic acid; for example, methyl(meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate,2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-octyl(meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate,tetradecyl (meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate,palmityl (meth)acrylate, and stearyl (meth)acrylate; other(meth)acrylates such as isobornyl (meth)acrylate, benzyl (meth)acrylate,phenyl (meth)acrylate, 2-bromoethyl (meth)acrylate, 2-phenylethyl(meth)acrylate, and 1-naphthyl (meth)acrylate, alkoxyalkyl(meth)acrylate, such as ethoxyethyl (meth)acrylate, mono-, di-, trialkylesters of ethylenically unsaturated di- and tricarboxylic acids andanhydrides, such as ethyl maleate, dimethyl fumarate, trimethylaconitate, and ethyl methyl itaconate. Preferred carboxylic acidmonomers include (meth)acrylic acid. Preferred comonomers are butyl(meth)acrylate, styrene, and methyl methacrylate. The aqueous tintingcomposition may contain from 0.1 to 40 weight %, preferably at least 0.5to 35 weight %, and more preferably, at least 0.75 to 30 weight % of atleast one select dispersing resin, based on the weight of the aqueoustinting composition. The level of dispersing resin in the aqueoustinting composition depends upon the type of pigment and the level ofpigment.

The select dispersing resin is characterized as having a hydrophobicitydefined by a Hansch parameter in the range of 2.1 to 6, preferably inthe range of 2.2 to 4, and more preferably in the range of 2.3 to 3.5.The Hansch parameter for a polymer is calculated using a groupcontribution method. The monomer units forming a polymer are assigned ahydrophobicity contribution and the relative hydrophobicities of thepolymer is calculated based on the weight average of the monomers in thepolymer. Hansch and Fujita, J. Amer. Chem. Soc., 86, 1616-1626 (1964);H. Kubinyi, Methods and Principles of Medicinal Chemistry, Volume 1, R.Mannhold et al., Eds., VCH, Weinheim (1993); C. Hansch and A. Leo,Substituent Constants for Correlation Analysis in Chemistry and Biology,Wiley, N.Y. (1979); and C. Hansch, P. Maloney, T. Fujita, and R. Muir,Nature, 194. 178-180 (1962).

Values of the hydrophobicity contributions for several monomers are listin Table 1.

TABLE 1 Monomer Hydrophobicity Contribution ethyl acrylate 2.11 butylacrylate 3.19 2-ethyl hexylacrylate 5.22 styrene 4.29 methylmethacrylate 1.89 ethyl methacrylate 2.43 butyl methacrylate 3.51isobornyl methacrylate 2.22 butadiene 4.0 acrylic acid −2.52 methacrylicacid −2.2 maleic anhydride −3.5

The acid number is the number of milligrams of KOH required toneutralize the acid contained in one gram of a material. The selectdispersing resin may have an acid number in the 65 to 150, preferably inthe range of 85 to 115, and more preferably in the range of 90 to 110.

The weight average molecular weight of the select dispersing resin maybe in the range of 5,000 to 100,000, preferably in the range of 10,000to 50,000, and more preferably in the range of 15,000 to 30,000. Theweight average molecular weight is determined by methylation of the acidgroups of the dispersing resin, followed by gel permeationchromatography using tetrahydrofuran as the solvent.

The polymerization techniques which may be used to prepare the selectdispersing resin are well known in the art. The select dispersing resinmay be prepared by emulsion polymerization and semibulk polymerization.The polymerization may be a redox or thermal initiation processemploying conventional free radical initiators, such as, for example,ammonium and sodium persulfates, hydrogen peroxide, benzoyl peroxide, ort-butyl peroctoate at levels typically of from 0.05 to 3% by weightbased on the total weight of monomer. Redox systems using the sameinitiators coupled with suitable reducing agents such as for exampleisoascorbic acid, sodium bisulphite, or sodium sulphoxylate formaldehydemay be used at similar levels. Surfactants may be included in thepolymerization process. Suitable surfactants include nonionic and ionicsurfactants. Chain transfer agents such as mercaptan, polymercaptan, andpolyhalogen compounds in the polymerization mixture may be used tomoderate the molecular weight of the select dispersing resin. Examplesof chain transfer agents which may be used include long chain alkylmercaptans such as t-dodecyl mercaptans, alcohols such as isopropanol,isobutanol, lauryl alcohol, or t-octyl alcohol, carbon tetrachloride,tetrachloroethylene, trichlorobromoethane. Generally from 0.1 to 6weight %, based on the weight of total monomer in the select dispersingresin, may be used. Alternatively, suitable molecular weights may beobtained by increasing the initiator level, or by a combination ofincreased initiator level and a chain transfer agent. The polymerizationprocess may be a batch, semicontinuous, or continuous process.

The select dispersing resin may be provided as a solid or neutralizedinto aqueous solution. Suitable bases to neutralize the selectdispersing resin include ammonium hydroxide, sodium hydroxide, potassiumhydroxide, triethanol amine, and diethanol amine. Ammonium hydroxide ispreferred.

The aqueous tinting composition contains at least 15 weight % water.Water miscible cosolvents such as ethylene glycol, propylene glycol,glycol ethers, isopropanol may be included. Preferably the aqueoustinting composition contains a total level of volatile organic compoundsin the range of 0 to 10 weight %, preferably 0 to 6 weight %, and morepreferably 0 to 4 weight %, based on the weight of the aqueous tintingcomposition. The pH of the aqueous tinting composition may be in therange of 7 to 10. The viscosity of the aqueous tinting composition ispreferably in the range of 100 to 10,000 cps as measured by a Brookfieldviscometer (Brookfield Engineering Co.) to allow easy handling andaddition of the aqueous tinting composition to an aqueous base paint.

The aqueous tinting composition may optionally contain other ingredientsincluding biocides; low molecular weight dispersants; extenders suchtalc and calcium carbonate; humectants such as hydroxyethyl celluloseand polysaccharides; thickeners; and surfactants. Preferably the typeand level of surfactant does not adversely affect the thickeningefficiency of associative thickeners in a material manner.

In one embodiment, the aqueous tinting composition is substantially freeof surfactant and contains from 0 to 5 weight %, 0 to 3 weight %, andmore preferably from 0 to 2 weight % surfactant, based on the weight ofthe aqueous tinting composition.

In one embodiment, the aqueous tinting composition is substantially freeof low molecular weight dispersant and contains from 0 to 3 weight %, 0to 1.5 weight %, and more preferably from 0 to 1 weight % dispersant,based on the weight of the aqueous tinting composition.

In another embodiment, the aqueous tinting composition is substantiallyfree of low molecular weight dispersant and substantially free ofsurfactant.

The aqueous tinting composition may also contain a macromolecularorganic compound having a hydrophobic cavity. These macromolecularcompounds may complex with surfactant to diminish the viscosity loweringeffect of the surfactant on the aqueous coating composition. Suitablemacromolecular organic compounds having a hydrophobic cavity includecyclodextrin, cyclodextrin derivatives, cycloinulohexose,cycloinuloheptose, cycloinulocotose, calyxarene, and cavitand.Cyclodextrin includes α-cyclodextrin, β-cyclodextrin, andγ-cyclodextrin. Cyclodextrin derivatives refers to (α-cyclodextrins,β-cyclodextrins, and γ-cyclodextrins in which at least one hydroxylgroup located on the rim of the cyclodextrin ring have beenfunctionalized with a substituent group such as methyl, acetyl,hydroxypropyl, and hydroxyethyl groups. Cyclodextrin derivatives alsoinclude cyclodextrin molecules with multiple substituent groupsincluding cyclodextrin molecules with more than one type of substituentgroup. Cyclodextrin derivatives do not include polymers with more thanone attached cyclodextrin ring. Preferred cyclodextrin derivatives aremethyl-β-cyclodextrin and hydroxypropyl-β-cyclodextrin.Methyl-β-cyclodextrin is the most preferred cyclodextrin derivative.

The cyclic oligosaccharides having a hydrophobic cavity, such ascycloinulohexose, cycloinuloheptose, useful in the composition andmethod of the invention are described by Takai et al., Journal ofOrganic Chemistry, 1994, volume 59, number 11, pages 2967-2975.

The calyxarenes useful in the aqueous tinting composition and method ofthe invention are described in U.S. Pat. No. 4,699,966, WO 89/08092;JP-A-88/197544 and JP-A-89/007837.

The cavitands useful in the aqueous tinting composition and method ofthe invention are described in Italian application 22522 A/89 and Moranet al., Journal of the American Chemical Society, volume 184, 1982,pages 5826-5828.

The non-cyclic polysaccharides useful in the aqueous tinting compositionand method of the invention are described in PCT application WO98/24821. Suitable non-cyclical polysaccharides include both unmodifiedpolysaccharides and modified polysaccharides which are partially ortotally derivatized on the hydroxyl groups.

The level of macromolecular organic compound having a hydrophobic cavityin the aqueous tinting composition may be in the range of 0 to 5 weight%, preferably from 1 to 4 weight %, and more preferably, from 2 to 3weight %, based on the weight of the aqueous tinting composition.

The aqueous tinting composition may be prepared by providing the selectdispersing resin in a neutralized into water. Base may be added to thewater prior to, during, or after the addition of the dispersing resin.Next, the pigment is dispersed into the water containing the neutralizedselect dispersing resin. High shear mixing may be employed to dispersethe pigment. The pH of the aqueous tinting composition is typically inthe range of 7 to 10.

The aqueous tinting composition of this invention may be added to anaqueous base paint to prepare an aqueous coating composition. Theaqueous tinting composition is added to change the color of the aqueousbase paint, or to modify the color or the appearance of a coatingprepared from the aqueous coating composition. The aqueous base paintcontains polymer binder and rheology modifier. The aqueous base paintmay be a neutral base paint useful for preparing deep tone-coatings. Theneutral base paint does not contain titanium dioxide or other materialswhich provide opacity. The aqueous base paint may also be a white basepaint useful for preparing opaque coatings. The white base paintcontains titanium dioxide. The titanium dioxide is contained in thewhite base paint as particles. The titanium dioxide particles typicallyhave an average diameter in the range of 80 nm to 250 nm and may have acoating of silica or a coating of alumina. Suitable forms of titaniumdioxide include rutile titanium dioxide and anatase titanium dioxide.The white base paint may contain titanium dioxide at a level of 58g/liter to 2034 g/liter (10 lbs/100 gal to 350 lbs/100 gal) of aqueousbase paint.

The aqueous base paint also contains a polymer binder. The polymerbinder is dispersed as polymer particles in the aqueous medium of theaqueous base paint and may have average particle diameters in the rangeof 20 nm to 1000 nm. Suitable polymer binders include acrylic(co)polymers, vinyl acetate polymers, vinyl/acrylic copolymers,styrene/acrylic copolymers, polyurethanes, polyureas, polyepoxides,polyvinyl chlorides, ethylene/vinyl acetate copolymers,styrene/butadiene copolymers polyester polymer, polyethers and the like,and mixtures thereof. The polymer binder may be provided as an aqueousdispersion such as an emulsion polymer. The polymer binder may be chosento provide a coating, which is prepared from the aqueous coatingcomposition, with properties such as adhesion to a substrate, gloss,abrasion resistance, and barrier properties such as moisture resistanceand solvent resistance. The level of binder in the aqueous base paintmay be in the range of 145 g/liter to 2034 g/liter (25 dry lbs/100 galto 350 dry lbs/100 gal) of the aqueous base paint.

The aqueous base paint also contain at least one rheology modifier tothicken the aqueous base paint and to modify the rheology to allowapplication on substrates without excessive splattering or dripping ofthe aqueous coating composition, or sag of the wet paint film. Typicallymore than one rheology modifier is added to a paint to provide anaqueous paint with the desired rheology. Suitable rheology modifiersinclude nonhydrophobically modified rheology modifiers such ashydroxyethyl cellulose (HEC), alkali soluble emulsions (ASE), andpolyvinyl alcohol; and hydrophobically modified rheology modifiers, alsoreferred to as associative thickeners, such as hydrophobically modifiedethylene oxide urethane block copolymers (referred to herein as “HEUR”),hydrophobically modified alkali soluble polymers includinghydrophobically modified alkali soluble emulsions (referred to herein as“HASE”), hydrophobically-modified celullosics, includinghydrophobically-modified hydroxyethyl cellulose (referred to herein as“HMHEC”), hydrophobically modified poly(acrylamide); and mixturesthereof. The rheology modifier may be present at a level of 5.8 g/literto 116 g/liter (1 lb/100 gal to 20 lb/100 gal) of the aqueous basepaint. A preferred aqueous base paint contains at least one associativethickener, which may be present in the aqueous base paint at a level ofat least 0.05% by weight of solids, based on the weight of the aqueousbase paint.

In one embodiment, the aqueous base paint is a low VOC compositioncontaining from 0 to less than 6% VOC by weight, preferably from 0 toless than to 3% VOC, and more preferably from 0 to less than 2% VOC,based on the total weight of the aqueous base paint. An aqueous coatingcomposition containing from 0 to less than 6% VOC by weight, preferablyfrom 0 to less than to 3% VOC, and more preferably from 0 to less than2% VOC, based on the total weight of the aqueous coating composition,may be prepared from an aqueous base paint having a low VOC composition.

The method of this invention includes the step of adding the aqueoustinting composition of this invention to an aqueous base paint toprepare an aqueous coating composition. This step is easily achieved bythe addition of the aqueous tinting composition with mixing.

The aqueous tinting composition and the method of this invention areuseful for improving the viscosity stability of an aqueous coatingcomposition, particularly upon the addition of the aqueous tintingcomposition to an aqueous base paint containing at least one associativethickener. The composition and method of the invention are not limitedby the type of pigment that is added to the aqueous coating composition.

The water-resistance properties, including blister resistance, wetadhesion, and scrub resistance of the compositions prepared using theaqueous tinting composition and method of this invention, are expectedto be improved because of the use of lower amounts of low molecularweight materials such as surfactants and dispersants, which may be usedrelative to conventional formulating techniques. Further, aqueouscoating compositions prepared using the aqueous tinting compositions andthe method of this invention, may react more predictably to addedaqueous tinting compositions, making color matching easier andfacilitating the use of software for color matching. Also, viscosityfluctuation in the aqueous coating composition is expected to bereduced. Further, the freeze-thaw stability of the aqueous coatingcomposition, the dispensing of the aqueous tinting composition (noclogs) and the sag resistance properties of wet films prepared fromaqueous coating compositions using the aqueous tinting compositions andmethod of the invention are expected to be improved.

The aqueous coating composition may be free of organic solvent or it maycontain a coalescing solvent. The aqueous coating composition maycontain typical coating additives such as fillers, defoamers,cross-linkers, catalysts, surfactants, stabilizers, anti-flocculants,coalescents, waxes, antioxidants, and suitable solvents, such as watermiscible solvents.

The aqueous coating composition of this invention may be applied bymethods well known in the art such as air-assisted spray, airless spray,plural component spray, brush, roller squeegee, roll coater, curtaincoater, and the like. Substrates to which the aqueous coatingcomposition may be applied include, for example, timber including butnot limited to cedar, pine, teak, oak, maple, and walnut; processedtimber including but not limited to medium density fiber board, chipboard, laminates; mineral substrates including but not limited tomasonry, concrete, stucco, fiber, mortar, cement, cement asbestos,plaster, plasterboard, glazed and unglazed ceramic; metal including butnot limited to galvanized iron, galvanized steel, cold rolled steel,aluminum, wrought iron, drop forged steel, and stainless steel;previously painted or primed surfaces (fresh, aged, or weathered)including but not limited to acrylic coatings, vinyl acrylic coatings,styrene acrylic coatings, powder coated surfaces, solvent acryliccoatings, alkyd resin coatings, solvent urethane coatings, and epoxycoatings; synthetic substrates including but not limited to polyvinylchloride, polyvinylidene chloride, polyethylene, and polypropylene;asphalt; cellulosic substrates such as paper, paperboard, wallpaper, andwallboard; glass; and leather. The aqueous coating composition may beused, for example, as a wood coating, maintenance coating, interior orexterior wall coating, metal primer or coating, plastics coating,traffic paint, leather coating, coil coating, architectural coating.Coatings prepared from the aqueous coating composition may be flatcoatings, satin coatings, semi-gloss coatings, gloss coatings, primer,textured coatings, and the like.

The aqueous tinting composition and method of the present invention areparticularly useful in systems employing delayed productdifferentiation, including tinting and mixing of the product componentsat the point-of-manufacture, point-of-sale or point-of-use, such asthose disclosed in U.S. Provisional Applications Serial No. 60/183,655filed Feb. 18, 2000, No. 60/183,656 filed Feb. 18, 2000, and No.60/247,639 filed Nov. 10, 2000.

All ranges used herein are inclusive and combinable. Some embodiments ofthe present invention will now be described in detail in the followingExamples.

The Krebs-Stormer viscosity was measured using ASTM method D562.

EXAMPLE 1

Preparation of Aqueous Tinting Compositions

Aqueous tinting composition were prepared containing the selectdispersing resins. The select dispersing resins were styrenated acryliccopolymers with the properties listed in Table 1.1

TABLE 1.1 Select Dispersing Resins Weight Average Select DispersingHansch Molecular Resin Parameter Acid Number Weight Example 1.1 2.17 9820,000 Example 1.2 2.81 98 20,000 Example 1.3 3.33 98 20,000

The select dispersing resins in Table 1.1 were provided as aqueoussolutions.

Green tinting compositions were prepared containing the materials listedin Table 1.2. The green aqueous tinting composition, Example G1, wasprepared using the select dispersing resin Example 1.1.

TABLE 1.2 Preparation of Green Tinting Compositions Example G1Comparative G Material (wt. %) (wt. %) diethylene glycol 22.91 23.00Water 12.55 19.5 defoamer 2.99 3.00 surfactant-1 0 3.50 surfactant-23.98 4.00 dispersant 1.49 1.5 extender-1 9.96 9.96 extender-2 24.9024.90 phthalo green pigment 9.96 9.96 ammonia (28%) 0.69 0.68 Water 1.060 Example 1.1 (40.7 wt %) 9.5 0

Green aqueous tinting compositions Example G2 and Example G3 wereprepared with dispersing resins Example 1.2 and Example 1.3,respectively, replacing select dispersing resin Example 1.1 in theExample G1.

Yellow tinting compositions were prepared containing the materialslisted in Table 1.3. The yellow aqueous tinting composition, Example Y1,was prepared using the select dispersing resin Example 1.1.

TABLE 1.3 Preparation of Yellow Tinting Compositions Example Y1Comparative Y Material (wt. %) (wt. %) glycol mixture 14.2 29.00 Water16.20 11.40 defoamer 2.00 2.00 surfactant 0 8.00 dispersant 1.5 2.0Yellow iron oxide pigment 49.10 49.10 ammonia (28%) 0.50 0.50 Example1.1 16.60 0

Yellow aqueous tinting compositions Example Y2 and Example Y3 wereprepared with dispersing resins Example 1.2 and Example 1.3,respectively, replacing select dispersing resin Example 1.1 in ExampleY1.

EXAMPLE 2

Preparation of Aqueous Base Paint

An aqueous base paint was prepared by first preparing a titanium dioxidegrind by combining the materials in the order listed in Table 2.1.

TABLE 2.1 Titanium Dioxide Grind Material Amount Water 53.11 g propylene glycol 1.70 g Tamol ™ 731 dispersant 1.00 g Triton ™ CR-10surfactant 0.07 g Foamaster ™ VL defoamer 0.10 g Kathon ™ LX (1.5%) 0.07g Rhoplex ™ SG-10M polymer binder 200.00 g  Ti-Pure ™ R-706 titaniumdioxide 25.00 g  Acrysol ™ RM-2020 NPR rheology modifier 10.00 g  Water50.00 g 

Kathon, Rhoplex, and Acrysol are trademarks of Rohm and Haas Company.

Foamaster is a trademark of Cognis Corp.

Triton is a trademark of the Union Carbide Co.

Ti-Pure is a trademark of E.I. DuPont de Nemours and Co.

Next, an aqueous base paint was prepared by combining the titaniumdioxide grind with the materials listed in Table 2.2.

TABLE 2.2 Aqueous Base Paint Formulation Material Amount Water 62.78 g Rhoplex ™ SG-10M polymer binder 403.13 g  Ropaque ™ Ultra plasticpigment 5.60 g Texanol ™ coalescent 30.33 g  ammonia (28%) 1.43 gAcrysol ™ RM-2020 NPR rheology modifier 14.24 g  Acrysol ™ RM-825rheology modifier 0.65 g Foamaster ™ VF defoamer 2.00 g water 25.00 g 

Ropaque is a trademark of Rohm and Haas Company.

Texanol is a trademark of Eastman Chemical Co.

The aqueous base paint had a PVC of 3.3% and a VS of 33.8%.

EXAMPLE 3

Preparation of Aqueous Coating Compositions

The aqueous coating compositions were prepared by mixing the aqueoustinting compositions into the aqueous base paint at a level of 93.7ml/liter (12 oz/gal). The Krebs-Stormer viscosity of the aqueous coatingcompositions were measured prior to and 24 hours after the addition ofthe aqueous tinting compositions.

TABLE 3.1 Viscosity Decrease for Aqueous Coating Composition ContainingAqueous Tinting Composition Coating Composition Tinting CompositionViscosity Change (KU) Example 3.1 Example G1 −13 Example 3.2 Example G2−3.4 Example 3.3 Example G3 −5.9 Comparative 3.A Comparative G −21.4Example 3.4 Example Y1 −17 Example 3.5 Example Y2 −6.9 Example 3.6Example Y3 −6.3 Comparative 3.B Comparative Y −50.7

The results in Table 3.1 show that the addition of the aqueous tintingcompositions of this invention, which contained the select dispersingresins, improved the viscosity stability of the aqueous coatingcompositions. In particular, the aqueous coating compositions containingthe green aqueous tinting compositions of this invention, Examples3.1-3.3, had viscosity decreases of 13 KU or less. In comparison, thecomparative coating composition, Comparative 3.A, which was tinted witha surfactant containing tinting composition, had a viscosity decrease of21.4 KU. For the aqueous coating compositions containing the yellowaqueous tinting compositions of this invention, Examples 3.4-3.6, theviscosity decreases were 17 KU or less. The comparative coatingcomposition, Comparative 3.B, had a viscosity decrease of 50.7 KU.

The results show that the aqueous tinting composition containing theselect dispersing resins and the method of preparing the aqueous coatingcompositions of this invention provide aqueous coating composition withimproved viscosity stability.

We claim:
 1. A method of improving the viscosity stability of an aqueouscoating composition upon the addition of an aqueous tinting composition,comprising the steps of: a) providing an aqueous base paint comprising:i) at least one polymer binder, iii) at least one rheology modifier; andb) adding to said aqueous base paint, said aqueous tinting compositioncomprising: i) at least one pigment; and ii) at least one selectdispersing resin having a Hansch parameter in the range of 2.1 to 6 andan acid number in the range of 65 to
 150. 2. The method according toclaim 1 wherein said select dispersing resin has a weight averagemolecular weight in the range of 15,000 to 40,000.
 3. The methodaccording to claim 1 wherein said select dispersing resin is prepared byemulsion polymerization.
 4. The method according to claim 1 wherein saidrheology modifier is an associative thickener.
 5. The method accordingto claim 1, 2, 3 or 4 wherein said aqueous tinting composition furthercomprises at least one macromolecular compound having a hydrophobiccavity.
 6. The method according to claim 1, 2, or 3 wherein said aqueoustinting composition comprises from 0 to 5 weight % surfactant.
 7. Anaqueous tinting composition comprising: a) from 2 to 70 weight % of atleast one pigment; and b) from 0.1 to 40 weight % of at least one selectdispersing resin having a Hansch parameter in the range of 2.1 to 6 andan acid number in the range of 65 to 150; based on the weight of saidaqueous tinting composition.
 8. The aqueous tinting compositionaccording to claim 7 wherein said select dispersing resin has a weightaverage molecular weight in the range of 15,000 to 40,000.
 9. Theaqueous tinting composition according to claim 7 wherein said selectdispersing resin is prepared by emulsion polymerization.
 10. The aqueoustinting composition according to claim 7, 8, or 9 comprising a totallevel of volatile organic compounds in the range of 0 to 10 weight %,based on the weight of said aqueous tinting composition.